1. Field of Invention
The present invention relates to an aromatic amine compound, and a light-emitting element, a light-emitting device, and an electronic appliance each using the aromatic amine compound.
2. Description of the Related Art
In recent years, research and development have been extensively conducted on a light-emitting element using a compound with a light-emitting property. In a basic structure of such a light-emitting element, a layer containing an organic compound with a light-emitting property is sandwiched between a pair of electrodes. By application of voltage to this element, electrons and holes are injected from the pair of electrodes to the layer containing an organic compound with a light-emitting property to cause current flow. Then, by recombination of these carriers (electrons and holes), the organic compound with a light-emitting property forms an excited state, and light is emitted when the excited state returns to a ground state. Because of such a mechanism, this kind of light-emitting element is called a light-emitting element of current excitation type.
A great advantage of such a light-emitting element lies in its thinness and lightness in weight because the light-emitting element is formed by, for example, an organic thin film with a thickness of about 0.1 μm. Moreover, another advantage thereof is high response speed because the time it takes for light emission after carrier injection is about 1 μs or shorter. In view of these advantages, it is considered that the light-emitting element is suitable for a flat panel display element.
Since the light-emitting element is formed into a film shape, surface light emission can be easily obtained by forming a large-area element. This is a feature which is difficult to be obtained in point light sources typified by an incandescent lamp and an LED or line light sources typified by a fluorescent lamp. Accordingly, the utility value of the light-emitting element is also high as a surface light source applicable to illumination and the like.
In order to overcome many problems derived from materials of such a light-emitting element and to improve its element characteristics, improvement of an element structure, material development, and so on are carried out.
For example, Nonpatent Document 1 describes a light-emitting element using a blue light-emitting material.    [Nonpatent Document 1] Meng-Huan Ho, Yao-Shan Wu and Chin H. Chen, 2005 SID International Symposium Digest of Technical Papers, p 802-805